FREQUENCY OF DIABETES IN FAMILY MEMBERS OF PROBANDS WITH NON-INSULIN-DEPENDENT DIABETES-MELLITUS

Objectives. To describe the prevalence of known diabetes in a multi-ethnic community in South Auckland, New Zealand, in relation to family history of diabetes and past history of diabetes in pregnancy. Design. A cross-sectional, household survey comparing ascertainment with local general practice diabetes registers where they existed. Setting. An inner-city community with a high proportion of Maori, Pacific Islands people and Europeans. Subjects. A total of 55 518 residents (91% response), Comparison with diabetes registers showed 91% ascertainment of known diabetic residents. More detailed interviews with 176/214 (82%) Europeans, 286/336 (85%) Maori and 495/585 (85%) Pacific Islands people with known diabetes, Fifty subjects had insulin-dependent diabetes mellitus on clinical criteria and were excluded from analyses. Main outcome measures. Prevalence of diabetes. Results. Those with non-insulin-dependent diabetes mellitus were more likely to have a diabetic mother than father (Europeans, 21.7% vs. 9.9%; Maori, 17.6 vs. 11.4%; Pacific Islands, 15.7 vs, 5.3%). Diabetic women had a similar likelihood of having a diabetic father as diabetic men but were 1.84 times as likely to have a diabetic mother (95% CI, 1.27-2.69). Diabetic women with past diabetes in pregnancy had 2.05 (95% CI, 1.01-4.15) times the chance of a diabetic offspring as women who had not had past diabetes in pregnancy, who in turn had 2.69 (95% CI, 1.17-6.18) times the likelihood of having a diabetic offspring as diabetic men. Conclusions. The mother is a more important conduit for inheritance of diabetes than the father in these three ethnic groups. A history of diabetes in pregnancy confers an extra risk to the offspring above this usual maternal excess.